@Paul_King1 Were you able to resolve this?
I may have encountered somewhat of a similar bug, but unclear if it is identical to the issue you flagged out here.
@Justin I was able to change the dropdown and select either day, week, month or year (1). After selecting day for example, I was able to save the plan successfully (2), However, upon revisiting the plan, no matter which billing cycle value I selected, it will always show as monthly (3). The value will be greyed out and locked in.
Checking Stripe | Products dashboard, the billing cycle reflects the chosen billing cycle ok. If day was selected, the interval shows it as daily. If week was selected, the interval shows it as weekly .. and so on.
Plugin version is 2.8.1, is this the latest?